The goal of the Center is to provide administrative and research facility support as well as small project grants to a group of MDIBL investigators whose research is directed at identifying how heavy metals (or metal compounds) interact at the molecular level with membrane transport systems to impair physiologic processes of importance to human health. The CMTS enables investigators to utilize marine species as unique alternative experimental models and facilities scientific collaborations and communications and training of biomedical scientists (clinicians and basic scientists, as well as students at all levels) in aspects of environmental toxicology of relevance to human health. Projects supported examine the mechanism of action of cadmium, cobalt, mercury, methylmercury and nickel on various membrane transport systems in tissues including hepatic, renal, rectal gland, bladder, intestine, and red cells. The current proposal focuses on 6 scientific groups chosen on the basis of scientific excellence and productivity during the previous period of project support, as well as a 7th newly recruited group. These projects and investigators include: 1) Mechanisms and Targets of Mercury's Impairment of Cell Volume Regulation in Skate Hepatocytes 2) Molecular Mechanisms of Mercury's Effects on the Thiazide-Sensitive, NACL Cotransporter in Flounder Urinary Bladder, 3) Effects of Cadmium, Cobalt and Nickel on Signal Transduction Pathways of Hormones Regulating Chlorides Secretion in Shark Rectal Gland; 4) Effects of Cadmium and Mercury on Na-K-C1-cotransporter in Shark Rectal Gland; 5) The Molecular Mechanism of Mercury Interaction with the Taurine Transport System of Red Blood Cells; 6) Mechanisms of Action of Mercury on Chloride Transport in Shark Rectal Gland and Rabbit Thick Ascending Limb; 7) Expression of ATP- Permeable Channels in Shark Rectal Gland Cells As a Phenotypic Response to Chronic Cadmium Intoxication.